See I think that is different. Your body is going to take a while to digest real foods, so in a sense its not uptaking the protien all at once. The protien threshold theory probably was meant when talking about protien powders other than casein like taking 60grams of whey in one serving. Unless your body was starved of protien i highly doubt it would absorb all 60grams. Probably piss it out. I do agree with it depending on numerous factors tho'
On the note of numerous factors, the metabolic fate of dietary protein is HIGHLY dynamic. And true, it varies according to the type of protein, be it powdered or animal flesh & the subtypes thereof.
But in the particular case of the body not being able to absorb 60g whey unless you're fasted, I think there's more to that bit of discussion. Unless you're truly fasted upon waking, there's always gonna be 'previous meal overlap' regarding absorption of the macros, unless your feeding frequency is 3x/d or less. With the typically high meal frequency in BB protocols the only true postabsorptive state is upon waking. Does this mean that 60g of whey in a single shot should be avoided elsewhere? I don't agree. Let's imagine a 200 lber is dieting down for a show, cutting carbs low, & taking in 300g protein/d (1.5g/lb). If you were to really nitpick & match intake with demand, it would actually benefit to have a 60g hit postW when protein turnover (the cycle of synthesis & degradation) is markedly higher than at any other point in the day. Heck if you want, you can have the other 240g at 6 other points in the day consisting of 40g hits.
I understand that we're batting around theoretics, & much of this stuff hasnt been measured, & thus the conjecture continues, so bear with me. I still think that assuming specific limits on absorption doesn't have enough basis. All protein gets absorbed. Whether it gets put to use for LBM accretion depends on a lot of factors. If it isn't used to create new lean tissue, the other possible scenarios are it's either oxidized for energy or stored as fat. This will depend on yet more variables, not the least of which is training state, acute & chronic energy balance, etc, etc.